Concluding three days of intense diplomatic talks with Iran along with members of the P5+1 group - the US, France, Germany, Russia, China and Britain - in Geneva, Kerry, however, cautioned against expecting too much at this point of time.
"We came to Geneva to narrow the differences. I can tell you without any exaggeration we not only narrowed differences and clarified those that remain, but we made significant progress in working through the approaches to this question of how one brings in a programme that guarantees this peaceful nature," Kerry told reporters in Geneva.
The two sides said the talks will resume on November 20.
"There's no question in my mind that we are closer now, as we leave Geneva, than we were when we came, and that with good work and good faith over the course of the next weeks, we can in fact secure our goal," he said.
"I am impressed and grateful for the way in which the P5+1 countries joined together and worked effectively together, the teams worked effectively together. And I think that tonight there was a unity in our position and a unity in the purpose as we leave here.
The two sides said the talks will resume on November 20. Any agreement would be a breakthrough after nearly a decade of mostly inconclusive discussions between the West and Iran since the Islamic Revolution of 1979.
The US and its five partners were seeking initial caps on Iran's capability to make a nuclear bomb, while Tehran sought some easing of sanctions hurting its economy.
"We are committed to have our political directors meet in the next days, and we are also committed to returning as necessary somewhere over the next weeks, hopefully, with the goal of either building on what was done today or completing the task," he said.
"Diplomacy takes time, and all the parties here need time to fully consider the issues very complicated, technical, difficult issues that we discussed here in the last days," he said.